/*
 * @(#)CombinerElement.java
 *
 * Copyright 2005 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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package org.wso2.balana.combine;

import org.wso2.balana.Indenter;
import org.wso2.balana.PolicyTreeElement;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import java.io.OutputStream;

/**
 * Represents one input (a Rule, Policy, PolicySet, or reference) to a combining
 * algorithm and combiner parameters associated with that input.
 * 
 * @since 2.0
 * @author Seth Proctor
 */
public abstract class CombinerElement {

	// the element to be combined
	private PolicyTreeElement element;

	// the parameters used with this element
	private List parameters;

	/**
	 * Constructor that only takes an element. No parameters are associated with
	 * this element when combining.
	 * 
	 * @param element
	 *            a <code>PolicyTreeElement</code> to use in combining
	 */
	public CombinerElement(PolicyTreeElement element) {
		this(element, null);
	}

	/**
	 * Constructor that takes both the element to combine and its associated
	 * combiner parameters.
	 * 
	 * @param element
	 *            a <code>PolicyTreeElement</code> to use in combining
	 * @param parameters
	 *            a (possibly empty) non-null <code>List</code> of
	 *            <code>CombinerParameter<code>s provided for general
	 *                   use (for all pre-2.0 policies this must be empty)
	 */
	public CombinerElement(PolicyTreeElement element, List parameters) {
		this.element = element;

		if (parameters == null)
			this.parameters = Collections.unmodifiableList(new ArrayList());
		else
			this.parameters = Collections.unmodifiableList(new ArrayList(
					parameters));
	}

	/**
	 * Returns the <code>PolicyTreeElement</code> in this element.
	 * 
	 * @return the <code>PolicyTreeElement</code>
	 */
	public PolicyTreeElement getElement() {
		return element;
	}

	/**
	 * Returns the <code>CombinerParameter</code>s associated with this element.
	 * 
	 * @return a <code>List</code> of <code>CombinerParameter</code>s
	 */
	public List getParameters() {
		return parameters;
	}

	/**
	 * Encodes the element and parameters in this <code>CombinerElement</code>
	 * into their XML representation and writes this encoding to the given
	 * <code>OutputStream</code> with indentation.
	 * 
	 * @param output
	 *            a stream into which the XML-encoded data is written
	 * @param indenter
	 *            an object that creates indentation strings
	 */
	public abstract void encode(OutputStream output, Indenter indenter);

}
